Hiking pants are an important purchase because they must serve a lot of purposes and still be comfortable. In addition to keeping you warm and dry, they should be breathable, durable, tear resistant, provide sun protection, and be roomy enough so you can fit a pair of long underwear underneath in colder conditions.

As discussed in Layering, in colder climates and in the mountains you’ll need long underwear, a Base Layer. Base Layer pants generally only need to be worn in fall and winter months, depending on where you live.

Decide what features you really need. If you hike in hot, dry climates, you’ll want to make sure your pants are breathable. Likewise, if you’re in colder, wetter climates, you’ll want a pair that is less breathable and provides some water repellancy (you’ll still need rain pants for downpours).
Make sure your hiking pants can be worn with layers. You’ll want to be able to wear your hiking pants over a pair of long underwear, and underneath a pair of rainpants. When that sudden downpour comes and it is time to zip on your rain pants, they better fit over your hiking pants!
Convertible hiking pants or not? Decide if you need pants that convert to shorts or capris, or neither. There are lots of options on the market: zip off legs so you can quickly switch to hiking shorts, button up capris so you can cool off on hot summer hikes, and regular old hiking pants that are just pants. Are you going to be hiking near poison ivy or oak? Are you going to be in mosquito country? Then you probably don’t need hiking shorts.
UPF sun protection. Hiking pants with a UPF rating will have a tighter fabric weave, so will provide better protection from harmful sun exposure. Learn more about the importance of UPF ratings and what it means.
Look for pants that have lots of pockets. There is always chapstick, sunscreen, snacks, cameras, and all sorts of gear that we want to keep handy. Having pockets in your hiking pants sure help make it easy to have the important items readily accessible.
Find pants that fit you! What is the point of buying hiking pants that aren’t comfortable? Plus, don’t you want to look cute hiking on the trail?